I've swapped by ISP-supplied Fritz!Box 7530 (running the latest v.25 firmware) to a 2nd hand ZyXEL VMG8924-B10A (de-ISPed) running stock 1.00(AAKL.28)C0 firmware as a modem + router +AP
These are my opinions, so YMMV. I'm approximately 600m from an Hauwei Cabinet
Things that are better on the 7530Ease of use and default setup (especially DHCP control)
Raw firewall and NAT performance (leading to better overall performance)
WiFi (stability and performance)
Inbuilt TDR tells you the connection length
Things that are better on the VMG8924-B10AConfiguration options
Logs!
Shell access
VDSL stability (so far)
Things that seem to be equal between the 7530 and VMG8924-B10ANegotiated bandwidth
Overall, if there are no broadband issues, I prefer the 7530. Multiple live connections on the same device are faster - this might just be a NAT/Firewall loading problem with the older processor on the 8924. But 7530 tuning options are minimal and the logs are very poor making analysis very difficult. For example, if there is a link-level drop, this is as much as you get in the logs:
Date HH:25:27 Internet connection established successfully. IP address: aaa.bbb.ccc.ddd, DNS server: aaa.bbb.ccc.ddd and aaa.bbb.ccc.ddd, gateway: aaa.bbb.ccc.ddd, broadband PoP: name
Date HH:24:54 DSL is available (DSL synchronized with 54321/4321 kbit/s).
Date HH:24:29 DSL synchronization starting (training).
Date HH:18:21 Internet connection cleared.
Date HH:18:21 PPPoE error: Timeout.
Date HH:18:07 DSL not responding (no DSL synchronization).
Date HH:17:28 Timeout during PPP negotiation.
Date HH:17:28 Internet connection cleared.
This makes it hard to understand what is going on.